Conventionally, in map data employed in car navigation systems, mobile phones, mobile information terminals and the like, road networks have been represented by nodes indicating points on roads and links indicating roads between the points as shown in Non-Patent Document 1. In other words, the road networks have been represented by a plurality of link strings that represent series of roads as series of links. The link strings include information about the nodes and links. In addition, each of the link strings has identical node information indicating the identity of the nodes, and the identical node information represents connection relationships between links of the road network.
In the conventional map data, to indicate traffic restrictions between the links at a node, an entrance link and exit link to and from the node is specified using traveling sequence of the nodes indicated by the identical node information. Besides, in the conventional map data, to associate route guidance data for guiding a route at an intersection with the nodes, information representing the storage positions of the route guidance data is provided in the nodes in the link string.
As related technology, Patent Document 1 discloses a difference update data creating apparatus for navigation, which accesses difference data associated with road data update efficiently, and enables normal navigation processing even when the difference data is reflected on the original road data. The difference update data creating apparatus has a first creating section and a second creating section: the first creating section not only indicates existing roads and their connection points, but also creates first road data indicating new roads and their connection points, which are updated according to a plurality of road data for navigation conforming to a prescribed format, and creates the difference update data including identical road data identical to second road data indicating the existing roads and their connection points connected to the new roads or to their connection points; and the second creating section creates merging data defining correspondence between the difference update data and a plurality of road data for each road or connection point together with deletion flags for deleting the second road data from the plurality of road data in the navigation processing.
Non-Patent Document 1: “KIWI Format Ver. 1.10”, KIWI Investigation Committee, 7.2. Road Data Frame.
Patent Document 1: Japanese patent application laid-open No. 2004-198321.
As described above, in the conventional map data, the identical node information provided for each node in the link string indicates the node in another link string, which is identical to the node of a particular link string. Sequentially following from a node of a particular link string to nodes of other link strings and returning to the first node according to the identical node information, all the nodes appearing in the course of this are decided as identical nodes. This makes it possible to recognize that the links in the link strings joined to each node are connected to each other. As the identical node information, are employed a link string number for designating a link string and a node number within the link string for designating the node. The link string number is the order in the link string sequence, and the node number in the link string is the order in the node sequence in the link string.
In the conventional map data arranged as described above, when updating the map data in accordance with elimination and addition of a link string or node, it is necessary to change the order of the link string sequence and the order of the node sequence in the link string, and to change the link string number and the node number in the link string along with the foregoing changes. In this case, the link strings arranged after the eliminated or added link string must be changed even if they are independent of the eliminated or added link string. Likewise, the identical node information about the nodes arranged after the eliminated or added node must be changed even if it has nothing to do with the eliminated or added node. This offers a problem of increasing the amount of data to be updated, and of requiring complicated update processing for updating the link strings or nodes.
In addition, the entrance link to the node and the exit link from the node are represented in order the node appears when the nodes are followed according to the identical node information. Since the order is changed by the elimination or addition of the link string appearing when following the nodes according to the identical node information, even when a link string having nothing to do with itself is eliminated or added, the information about traffic restrictions from an existing entrance link to an exit link must also be changed. This also presents a problem of increasing the amount of data to be updated, and of complicating the update processing.
Besides, the map data includes route guidance data providing guidance information at intersections as node related information, and each node in the link string is provided with address information indicating the storage position of the route guidance data. Thus, the elimination or addition of the node or link changes the storage positions of the existing route guidance data. Accordingly, the address information indicating the storage positions of the route guidance data in the existing link strings must be changed. This presents a problem of increasing the amount of data to be updated, and of complicating the update processing.
The present invention is implemented to solve the foregoing problems. Therefore it is an object of the present invention to provide a map information processing apparatus and storage medium of the map information capable of reducing the amount of data instructing the update when a road or intersection is added or eliminated, and capable of carrying out the update processing simply and quickly.